There is known an image forming apparatus such as laser printers, in which a developing cartridge is detachably mounted to a main body of the apparatus.
The developing cartridge includes a developing roller and a supply roller for supplying toner to the developing roller. A shaft of the developing roller is rotatably supported by a developing frame that configures a housing of the developing cartridge. In addition, a shaft of the supply roller is rotatably supported by the developing frame, and a circumferential surface of the supply roller contacts a circumferential surface of the developing roller.
As long as the supply roller contacts the circumferential surface of the developing roller, it is not necessary to position the supply roller in an axial direction with high precision. However, when the supply roller is highly moved in the axial direction, the supply roller may contact another member in the developing cartridge or toner may not be supplied to a part within a range corresponding to a printing area of the developing roller, so that an inferior developing may occur.